// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef BASE_DEBUG_STACK_TRACE_H_
#define BASE_DEBUG_STACK_TRACE_H_

#include <stddef.h>

#include <iosfwd>
#include <string>

#include "base/base_export.h"
#include "build/build_config.h"

#if defined(OS_POSIX)
#include <unistd.h>
#endif

#if defined(OS_WIN)
struct _EXCEPTION_POINTERS;
struct _CONTEXT;
#endif

#if defined(OS_POSIX) && (defined(__i386__) || defined(__x86_64__) || (defined(__arm__) && !defined(__thumb__)))
#define HAVE_TRACE_STACK_FRAME_POINTERS 1
#else
#define HAVE_TRACE_STACK_FRAME_POINTERS 0
#endif

namespace base {
namespace debug {

    // Enables stack dump to console output on exception and signals.
    // When enabled, the process will quit immediately. This is meant to be used in
    // unit_tests only! This is not thread-safe: only call from main thread.
    // In sandboxed processes, this has to be called before the sandbox is turned
    // on.
    // Calling this function on Linux opens /proc/self/maps and caches its
    // contents. In non-official builds, this function also opens the object files
    // that are loaded in memory and caches their file descriptors (this cannot be
    // done in official builds because it has security implications).
    BASE_EXPORT bool EnableInProcessStackDumping();

    // A stacktrace can be helpful in debugging. For example, you can include a
    // stacktrace member in a object (probably around #ifndef NDEBUG) so that you
    // can later see where the given object was created from.
    class BASE_EXPORT StackTrace {
    public:
        // Creates a stacktrace from the current location.
        StackTrace();

        // Creates a stacktrace from an existing array of instruction
        // pointers (such as returned by Addresses()).  |count| will be
        // trimmed to |kMaxTraces|.
        StackTrace(const void* const* trace, size_t count);

#if defined(OS_WIN)
        // Creates a stacktrace for an exception.
        // Note: this function will throw an import not found (StackWalk64) exception
        // on system without dbghelp 5.1.
        StackTrace(_EXCEPTION_POINTERS* exception_pointers);
        StackTrace(const _CONTEXT* context);
#endif

        // Copying and assignment are allowed with the default functions.

        ~StackTrace();

        // Gets an array of instruction pointer values. |*count| will be set to the
        // number of elements in the returned array.
        const void* const* Addresses(size_t* count) const;

        // Prints the stack trace to stderr.
        void Print() const;

#if !defined(__UCLIBC__)
        // Resolves backtrace to symbols and write to stream.
        void OutputToStream(std::ostream* os) const;
#endif

        // Resolves backtrace to symbols and returns as string.
        std::string ToString() const;

    private:
#if defined(OS_WIN)
        void InitTrace(const _CONTEXT* context_record);
#endif

        // From http://msdn.microsoft.com/en-us/library/bb204633.aspx,
        // the sum of FramesToSkip and FramesToCapture must be less than 63,
        // so set it to 62. Even if on POSIX it could be a larger value, it usually
        // doesn't give much more information.
        static const int kMaxTraces = 62;

        void* trace_[kMaxTraces];

        // The number of valid frames in |trace_|.
        size_t count_;
    };

#if HAVE_TRACE_STACK_FRAME_POINTERS
    // Traces the stack by using frame pointers. This function is faster but less
    // reliable than StackTrace. It should work for debug and profiling builds,
    // but not for release builds (although there are some exceptions).
    //
    // Writes at most |max_depth| frames (instruction pointers) into |out_trace|
    // after skipping |skip_initial| frames. Note that the function itself is not
    // added to the trace so |skip_initial| should be 0 in most cases.
    // Returns number of frames written.
    BASE_EXPORT size_t TraceStackFramePointers(const void** out_trace,
        size_t max_depth,
        size_t skip_initial);
#endif // HAVE_TRACE_STACK_FRAME_POINTERS

    namespace internal {

#if defined(OS_POSIX) && !defined(OS_ANDROID)
        // POSIX doesn't define any async-signal safe function for converting
        // an integer to ASCII. We'll have to define our own version.
        // itoa_r() converts a (signed) integer to ASCII. It returns "buf", if the
        // conversion was successful or NULL otherwise. It never writes more than "sz"
        // bytes. Output will be truncated as needed, and a NUL character is always
        // appended.
        BASE_EXPORT char* itoa_r(intptr_t i,
            char* buf,
            size_t sz,
            int base,
            size_t padding);
#endif // defined(OS_POSIX) && !defined(OS_ANDROID)

    } // namespace internal

} // namespace debug
} // namespace base

#endif // BASE_DEBUG_STACK_TRACE_H_
